Syllabus Edition

First teaching 2014

Last exams 2024

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Enzymes (DP IB Biology: SL)

Exam Questions

3 hours35 questions
1a1 mark

State the reason why enzymes are referred to as biological catalysts. 

1b3 marks

The image below shows a representation of an enzyme-controlled reaction.

enzyme-substrate-complex

Describe the events taking place in the image.

1c2 marks

State what is meant by the term 'enzyme specificity'?

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2a2 marks

A student wanted to investigate the effect of substrate concentration on the activity of an enzyme called catalase. Catalase is an enzyme that commonly occurs inside living cells where it breaks down toxic hydrogen peroxide into oxygen and water. The image below shows the experimental set up done by the student.

catalase-and-hydrogen-peroxide-investigation-sq

List two control variables that the student would need to be aware of in the experiment shown in the image.

2b
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1 mark

The student decided to make up solutions at five different hydrogen peroxide concentrations. Their measurements for these solutions are shown in the table below.

Concentration of hydrogen peroxide solution (%) Volume of hydrogen peroxide required (cm3) Volume of distilled water required (cm3)
10 10 90
8 B C
6 6 94
A 4 96
2 2 98

Give the measurements needed to fill in gaps A-C in the table. 

2c1 mark

After measuring out the range of hydrogen peroxide concentrations shown in part (b), the student carried out the experiment using the equipment set up in part (a). They recorded the volume of oxygen (the product) produced after one minute, and repeated this measurement three times at each concentration. Their results are shown in the table below.

results-table-for-catalase-experiment

Use the data in the table to calculate the value missing from the square marked X. 

2d2 marks

State the purpose of repeating the experiment three times at each concentration of hydrogen peroxide. 

2e4 marks

Using the data in part (c), draw a graph of hydrogen peroxide concentration against the mean volume of oxygen. 

2f2 marks

Deduce the conclusions that can be drawn from your graph from part (e). 

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3a
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2 marks

A researcher investigated the effect of pH on the activity of stomach enzyme pepsin. 

Their results are shown in the image below. 

pepsin-rate-of-reaction-at-different-ph-sq

The rate of reaction can be calculated by using the following formula:

reaction space rate space equals space fraction numerator Amount space of space product space produced space left parenthesis straight g space dm to the power of negative 3 end exponent right parenthesis over denominator Time space left parenthesis straight s right parenthesis end fraction

Calculate the rate of reaction at pH 4. Give your answer with the correct units.

3b2 marks

Describe the differences between the curves at pH 2 and pH 4.

3c1 mark

State why product production at pH 2 does not continue indefinitely but reaches a plateau at around 14.75 g.

3d3 marks
(i)

Predict the outcome if the pH were increased to pH 10.

[1]

(ii)

Explain your answer at part i).

[2]

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4a2 marks

State two benefits of using immobilised enzymes in industrial processes.

4b3 marks

An example of the use of immobilised enzymes in industry is in the production of lactose-free milk. 

(i)

Identify the enzyme used in this process.

[1]

(ii)

State the substrate and products of the reaction.

[2]

4c2 marks

When the enzymes are immobilised for this process they are fixed to small alginate beads. The substrate solution is then poured through the beads in order for the substrate to react with the enzyme. 

State the benefits of having a large number of small beads for this process, as opposed to a small number of large beads. 

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5a4 marks

One mark is available for clarity of communication throughout this question. 

Describe the processes that occur during an enzyme-catalysed reaction. 

5b4 marks

Outline the events that occur when enzymes are exposed to high temperatures. 

5c3 marks

List three methods that can be used to immobilise enzymes.

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1a3 marks

Lipase is an enzyme that breaks down lipids. The diagram below shows an experiment set up by a teacher to investigate the effect of lipase concentration on the hydrolysis of lipids.

The pH of beaker B is measured for 3 minutes at the start of the experiment. Beaker A containing lipase solution is added to beaker B. The data logger recorded the change in pH over the next 5 minutes.

q1a-2-4-enzymes-medium-ib-hl-biology-sq

State, with a reason, the predicted change in pH after the lipase has been added. 

1b2 marks

State two variables that must be controlled to carry out the experiment in part (a) accurately and reliably.

1c3 marks

For the experiment in part (a), draw a results table that could be used to record the results of the investigation. Your table should include suggested enzyme concentrations, and units should be stated. 

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2a2 marks

A protease is an enzyme that digests protein. A research scientist isolated protease C from a particular species of bacteria. The researcher investigated the effect of temperature on the rate of hydrolysis of a protein by protease C.  The unprocessed results can be seen in the table below.

Temperature / °C Mass of protein hydrolysed after 4 minutes / mg

Rate of hydrolysis /

10 470  
15 990  
20 1180  
25 1310  
30 1030  
35 420  
40 110  

Calculate (with appropriate units) the missing details in the table above.   

 

2b4 marks

Draw a graph of the results seen in part (a). Your graph should include an accurate scale and correct axis labels. q2b-2-4-enzymes-medium-ib-hl-biology-sq

2c1 mark

Suggest how the research scientist controlled the pH throughout the experiment.

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3a2 marks

Explain the aspect of enzyme and substrate structure that enables successful catalysis of a biochemical reaction.

3b1 mark

The sketch graph below shows how the rate of an enzyme-catalysed reaction varies for two separate independent variables. For curve A the independent variable is the concentration of enzyme.

 q3b-2-4-enzymes-medium-ib-hl-biology-sq

Identify the independent variable for Curve B.

3c3 marks

The sketch graph below shows how the rate of an enzyme-catalysed reaction varies as temperature changes. q3c-2-4-enzymes-medium-ib-hl-biology-sq

Explain the rates of reaction at positions A, B, and C on the curve. 

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4a1 mark

Enzymes can be used in various industrial processes.

Suggest one reason why the use of enzymes in industry offers a commercial benefit over non-enzymatic processes.

4b3 marks

The diagram below shows a typical packed-bed immobilised enzyme reactor for a continuous production process in the food industry.q4b-2-4-enzymes-medium-ib-hl-biology-sq

State three benefits of using immobilised enzymes, as opposed to enzymes that are allowed to mix freely with the substrate.

4c2 marks

The process of binding an enzyme to an immobile matrix for the purposes of enzyme immobilisation has, in some cases, led to a reduction in the enzyme's activity level.

Suggest, with a reason, how the process of immobilisation could cause the change in enzyme activity after immobilisation.

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5a7 marks

One mark is available for clarity of communication throughout this question.

The sketch graph below shows the effects of varying the level of the independent variable, X, on the rate of an enzyme-controlled reaction. Lines A, B, and C represent three different independent variables which could be X.q5a-2-4-enzymes-medium-ib-hl-biology-sq 

(i)
Identify the independent variables that would cause lines A, B, and C.

 

(ii)
Use your knowledge of enzyme activity to explain the changes in reaction rate shown by lines A, B and C.
5b4 marks

Outline the method used in the production of lactose-free milk from dairy milk. 

5c4 marks

An experiment was set up to investigate the effect of temperature on an enzyme-catalysed reaction in which the reaction mixture changes from clear-colourless to clear-dark blue as the reaction progresses.

Describe:

(i)
How the independent variable in the experiment could be controlled.

(ii)
How a colorimeter could be used to measure colour change.

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1a1 mark

Certain plants that reproduce sexually contain an enzyme called pyrophosphatase. This enzyme plays a role in ensuring self-incompatibility, which is a mechanism that prevents a plant from fertilising itself. The selective advantage of self-incompatibility is that more cross-breeding can occur within a species, which has long term benefits for evolution and for maintaining a large pool of alleles.

Known volumes of pyrophosphatase and substrate can be mixed in a cuvette with a dye that starts as colourless and develops into a blue colour over time. The rate of colour development can be measured in a colorimeter by measuring the absorbance of light at a wavelength of 620 nm (red light). 

The graph shows the mean rate of reaction of pyrophosphatase measured over five repeats at 20°C.

mean-rate-of-reaction-of-pyrophosphatase-graph-sq

State why the wavelength of 620 nm was selected for this experimental measurement.

1b
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3 marks

Use the graph from part (a) to calculate the rate of the reaction at 100 seconds. Give your answer in suitable units. 

1c2 marks
(i)

Predict the effect that a higher enzyme concentration at the start of the experiment would have on the results calculated in part (b).

[1]

(ii)

Explain your answer in part (i).

[1]

1d3 marks

As the temperature increases, the rate at which pyrophosphatase works also increases up to a point, before decreasing. 

Explain why these changes in the reaction rate take place.  

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2a4 marks

In humans, the enzyme sucrase hydrolyses sucrose. This reaction occurs in the small intestine at 37°C.

(i)

Explain why sucrase can only hydrolyse sucrose.

[2]

(ii)

Describe how sucrase enables this reaction to take place at normal body temperature.

[2]

2b3 marks

A solution containing sucrose and sucrase was divided equally between two test tubes. One test tube (A) was heated to a temperature of 85°C, and the other (B) was kept at 37°C, as shown in the diagram below. Both test tubes were monitored for 30 minutes.

h-2b

 

(i)

Identify which test tube(s) would contain monosaccharides.

[1]

(ii)

Explain your answer in part (i).

[2]

2c2 marks

Suggest two sources of error that could arise from an experiment to measure the effect of temperature on the rate of an enzyme-controlled reaction.

Assume that in this experiment, the dependent variable is measured as the volume of a gas produced.  

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3a3 marks

A significant amount of research has been conducted on the enzyme composition of extremophile microorganisms, in order to discover new enzymes that can be used in the home in extreme conditions. One such organism, Planococcus halocryophilus, is a psychrophile (it grows at cold temperatures around 0°C). Trials with the enzymes of P. halocryophilus have discovered applications of these enzymes in the detergent industry. 

Suggest how these trial results are encouraging for the laundry detergent industry.  

3b3 marks

Many commercially-produced biological laundry detergents contain a range of different enzymes.

Explain why a range of enzymes can improve the detergent’s performance in the home. 

3c2 marks

Papain is a proteolytic enzyme derived from the papaya fruit. It has been used in contact lens cleaning solutions to remove denatured protein-containing deposits that accumulate on the surfaces of contact lenses during long periods of wear. The periodic removal of protein deposits increases wearer comfort and extends the wearing time.

The main protein component of tear film fluid is lysozyme.

Suggest a reason for the presence of lysozyme in tear film fluid.  

3d2 marks

Lysozyme and other proteins present in tear film fluid can denature rapidly when in contact with contact lens material. This denatured material loses its original function and forms deposits on the lens surface.

(i)

Describe the mode of action of papain against the denatured protein deposits on the surfaces of the contact lenses.

[1]

(ii)

Explain the effect that the action of papain would have on these contact lens deposits.

[1]

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4a1 mark

The enzyme glucoamylase is a catabolic enzyme that hydrolyses the α-1,4 glycosidic bonds in starch to produce glucose for use in industry. 

The enzyme used in this process can be covalently bonded to a substrate of beads to become immobilised. Once immobilised they are able to be used in 11 successive cycles before they need to be replaced. 

Suggest a potential method that could be used to determine whether the immobilised enzymes need to be replaced. 

4b4 marks

Glucoamylase has an optimum temperature of 60°C when free in solution, however when it is immobilised the optimum temperature is raised to between 60°C and 80°C.

Explain why this is an advantage to the manufacturers using this immobilised enzyme to produce glucose. 

4c2 marks

Some scientists think that the reason for the increase in optimum temperature of the immobilised enzyme is due to the covalent bonding between the enzyme and the beads that hold them in position. They believe that covalent bonding helps to reduce the influence of high kinetic energy on the bonds within the enzyme structure. 

Suggest how this would cause the enzyme to have a higher optimum temperature. 

4d2 marks

One of the sources of glucoamylase for this process is from a species of fungi called Aspergillus niger. 

Aspergillus niger is a saprotroph. 

Suggest two advantages of using saprotrophic fungi as a source of enzymes for the industry. 

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5a3 marks

One mark is available for clarity of communication throughout this question. 

Outline how changes in substrate concentration affects the rate of enzyme action. 

5b5 marks

Sometimes the active site of enzymes can be blocked or "inhibited" by substances that aren't the specific substrate for that enzyme. 

Suggest how this would affect the rate of reaction of an enzyme-catalysed reaction as well as some possible uses of enzyme inhibitors in medicine. 

5c7 marks

Plan an investigation to determine how changing the temperature of amylase affects the rate of reaction of the digestion of starch to maltose. 

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